I'm just guessing here, but it seems like Unity itself is building armv6 assembly. So I doubt you'll see any speed increases by using armv7 compiling. (Which is a shame since armv7 on newer devices is faster, and they added faster floating point support to thumb code.)
Obviously the newer devices can run armv6 code, as otherwise they wouldn't be able to run the old apps.
I'm assuming the reason you're bringing this up is because of this warning:
Of course it's just a warning and not an error. I turned off building for armv7 by using "standard" architectures (armv6 only) and it still runs on my iPad, so I'm guessing it can be ignored.
(I don't really have an answer for you.)
answered Jun 15 '10 at 10:45 PM